New data is shining a light on the state of Wellington's train network.

Over the past week, services in the capital have been slashed in half after a series of scheduling and equipment issues from KiwiRail.

But data released to Newstalk ZB shows the number of unplanned bus replacements of trains has been tracking up over the past two years.

Between March 2021 and March 2022 there were just over 1800 train services replaced by buses.

But in the following year that number more than doubled to 4810 bus replacements for trains.

A lack of redundancies is being highlighted as a major issue for the Wellington rail network.

Metlink General Manager, Samantha Gain says a high level of staff unavailability at the beginning of last year and early this year contributed to the increase.

Greater Wellington Regional Council Chair, Daran Ponter says factors like ice and slips contribute to the bus replacements.

"But I think the thing that probably has increased in that period has been absenteeism and staff shortages."

Daran Ponter explained the whole network is served by a few thin rail lines, which causes problems.

"If any part of that line is not usable, the entire line is down. There's no workaround. We are more fragile just by the very nature of the network."

Hutt Valley commuter Megan Fermo  says the current state of rail in Wellington is shocking.

"I think for New Zealand's capital, it's definitely not good enough in my eyes. I feel like it's sub-par."

Megan Fermo  says she was recently talking to a friend about the issues.

"She's from Norway, and she was saying that if they were to compare the trains over there to here, it's shocking. It's like something from the 80s or 70s."